To pursue accurate rectilinear movement is frequently seen in sports such as basketball, billiard, golf and etc. and preciseness completely depends on if the movement is accurate. A common feature of these sports is that the direction of the movement is initialed with a little deviation results in a great inaccuracy of the movement.
Taking the golf as an example, when the player pushes the golf ball into the hole, it is required to move rectilinearly toward the hole so that how to allow the ball moving toward orientation of hole and entering the hole is subject the player has to practice. For a new learner, it is necessary to learn a posture of holding the club with a movement along the same direction without deviation. It is an important factor that the learner has to control steadiness of direction during hands moving the club.
In addition, it is known that skill comes from practice and movements of human body can reach least mistake through practicing repeatedly. Little movement like reckoning by abacus or playing musical instruments with fingers and large movement like moving the whole hand or leg need to practice repeatedly in order to obtain the accuracy. Hence, the movement keeping in the same direction while the club has to be practiced repeatedly, otherwise it is hard to adjust error effectively and the progress through practice is very little.